My lab recently purchased both the Sigma (F9765) and Cayman (70440) Filipin reagents. These reagents were resuspended in DMSO in the hood in the dark and aliquoted to avoid freeze/thaw. Stock solutions are stored at -20. I found that both Filipin reagents worked great the first time I used them, but now a time-dependent loss in cholesterol signal intensity has occurred. Every time I go to use a new aliquot, it seems like it has weaker signal than the last tube. The reagents are only roughly 3 weeks old. I am using a NPC1 patient fibroblast cell line (which usually has very robust Filipin staining signal) for these tests, and the signal is now barely detectable. It seems there is rapid degradation of the Filipin reagents just by sitting in the -20. Has anyone else faced these issues?
Hello Josh Lorenz-Guertin
I recently started using filipin for few stains with NPC1 patient KO fibroblasts and had a similar issue. The only way to overcome this (so I heard), is to aliquot filipin under inert gas conditions. My collaborators have told me that filipin is very light-sensitive but also oxygen sensitive. So filipin aliquots should be used ASAP when aliquoting in the open air, or can be stored for longer if aliquoted under inert gas conditions. However, I have not confirmed this myself yet, but I do trust my collaborators since they have used filipin extensively. Hope this helped :)
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